Gas cooking appliance

ABSTRACT

A gas cooking appliance ( 1 ) comprises a support frame ( 2 ), at least one burner ( 3 ) rigidly connected to said support frame, and a gas feeding circuit ( 4 ) to feed gas to the burner, wherein at least one of the following components of the gas cooking appliance is made of a thermosetting or thermoplastic material: •at least one burner body, being part of said at least one burner; •a spark plug body, being part of said at least one burner; •at least one gas connection pipe, being part of said gas feeding circuit, to feed gas to said at least one burner; •a gas rail, being part of said gas feeding circuit, connected to said at least one gas connection pipe; •a connection member, being part of said gas feeding circuit, for connecting the gas rail to an external feeding pipe; and •at least part of the support frame.

The present invention relates to a gas cooking appliance, such as a gascooktop (or cooking hob) or a free standing cooker.

Typically, a gas cooking appliance comprises one or more burners rigidlyconnected to a supporting and protective structure, and a gas feedingcircuit to feed gas to the burner(s).

A cooktop, in particular, typically comprises a supporting plate orframe of rectangular shape and having a plurality of seats, a pluralityof burners positioned in the seats and fixed to the supporting frame,and a gas feeding circuit, to feed combustion gas to the burners. Theseparts are typically assembled with each other so as to form a singlerigid body.

In turn, each burner typically comprises a burner body fixed to thesupporting frame, a burner crown held by the burner body and havingcircumferential openings for the exit of the air-gas combustion mixture,a cap closing the burner top, a gas injector to eject a gas flow intothe burner body, a tubular element (typically integrated in the burnercrown) for air/gas mixing by means of the Venturi effect, a thermocoupleand a spark plug support (also usually integrated in the burner crown).

These burners may have different dimensions, as well as different sizeof the burner ports so as to achieve different velocity, pressure,inclination and distribution of the air-gas mixture. Moreover, it ispossible to have more complex burner structures, with two or even threeflame crowns.

The gas feeding circuit typically comprises a gas rail extending alongone side of the supporting frame and designed to be connected to anexternal gas feeding pipe, a plurality of valves distributed along thegas rail in a number corresponding to the number of burners, acorresponding number of gas pipes connecting the gas rail to the burnervia the valves, and a plurality of joints (typically “elbow”, “push on”and “Boule and nut” connectors), to connect each other the external gasfeeding pipe with the gas rail, the gas rail with the valves, the valveswith the pipes, and the pipes with the burners.

Typically, the cooktop also comprises a top plate, which is positionedonto the supporting frame to define therebetween a space where the gasfeeding circuit is arranged.

All these components are necessarily made of a heat-resistant material.In particular, the burners are typically made of die cast aluminium,which is safe, easy to cast and long lasting. The other above-mentionedparts of the appliance, like the connection pipes, the gas valves andthe main rail, are usually made of aluminium, zinc plated, iron orbrass.

The mass production of this kind of appliance has demonstrated theexistence of some drawbacks, such as the high number of theconstructional components, the time needed to assembly them, as well asthe complexity of the die casting process to produce the burners and theresulting increase of the overall production costs, since the diecasting tooling has a limited duration over time, and a high cost ofenergy consumed. Moreover, it has been observed that some parts of theappliance made of the above-mentioned materials may have a limitedduration and may deteriorate due to corrosion or cleaning agents.

Some of these drawbacks have already been highlighted in the patentliterature.

US2003000512 points out that a major drawback of typical burners made ofa plurality of pieces assembled together is that they have a largenumber of constructional components, so that a significant amount oftime is required to assemble the individual components as a single unit,and then to assemble the burners on the cooking hobs. The samedifficulties exist when the burner must be assembled or disassembled formaintenance or routine cleaning purposes.

The same document highlights that the production of the individualcomponents by means of die-casting processes is complex and increasesthe overall production costs, and that the material used, typicallypressure-cast aluminium, has a limited duration and is subject tocorrosion by the cleaning agents.

The document then suggests, in order to overcome these problems, torealize a gas burner for a cooking hob wherein a burner body, aflame-dividing element defining together with said burner body anair/gas mixing chamber, and a converging/diverging duct defining aVenturi tube located downstream of a gas injector, are part of amonolithic structure in the form of a pressed sheet-metal casing, inparticular made of steel.

However, such solution, although being relatively safe and cheap, can beused only in limited circumstances because of the material used. Inparticular, it can be implemented only in very simple types of gasburner, which perform the minimum and essential functions of any gasburner. In addition, the problem of assembling the burner with aplurality of other parts still exists.

Another solution for making the production process of a cooking hobeasier and cheaper is suggested by EP0615096A1, which describes acooking plateau for a gas device made of a heat-resistant material, suchas glass, plastic, aluminium, or ultra-deep drawn steel. The cookingplateau integrates burner housings, pan supports, and hinge points, soas to have a single plate-shaped part suitable to achieve differentfunctions.

However, this solution offers only a limited advantage, as it concernsonly the plateau, while all the other parts are still made according toknown techniques, with the same materials and design. Therefore theoverall production process is still subject to the above-mentioneddrawbacks.

It would therefore be desirable, and it is actually a main purpose ofthe present invention, to provide a gas cooking appliance that can bemanufactured and assembled/disassembled in an easier and less expensiveway than the cooking appliances of the prior art.

The Applicant has found that by making one or more parts of a gascooking appliance of a thermosetting or thermoplastic material by aninjection moulding process it is possible to reduce the productioncosts, since the cost per single piece is lower and it is possible tointegrate some of these parts in a single piece by the same mouldingprocess. Moreover, by integrating some parts together in a single piecethe overall production process can be sensibly simplified and the finalgas cooking appliance can be easier to assemble/disassemble.

A thermosetting material (or thermo-set) is a polymer material for whichit is not possible to define a melting point, and a progressive increasea temperature would not result in its melting but instead in its burn.In particular, the material is a resin consisting of at least twomonomers bound together to form a polymer through branching(cross-linking process) under the action of a catalyst activated by atemperature increase.

Differently, for a thermoplastic material there is no cross-linkingprocess, and the polymeric chains overlap one onto the other without aprecise order (or with a predetermined orientation in the case ofsemi-crystalline structures) and without chemical constraints, so thatin this case a melting point can be defined.

In particular, according to the present invention, at least thefollowing parts can be advantageously made of a thermosetting orthermoplastic material:

-   -   the supporting frame or part thereof;    -   the burner bodies;    -   the gas rail;    -   the spark plug body (insulation body);    -   the connection elements that connects the rail to an external        feeding pipe for receiving gas; and    -   the connection pipes feeding the gas from the rail to the        burner.

Moreover, two or more of these parts can be integrated in a single pieceof thermosetting or thermoplastic material by a single injectionmoulding process. Possibly, all these parts may be realized as a singlepiece.

In a first aspect thereof, the present invention thus relates to a gascooking appliance, comprising a support frame, at least one burnerrigidly connected to the support frame, and a gas feeding circuit tofeed gas to the burner, wherein at least one of the following componentsis made of a thermosetting or thermoplastic material:

-   -   at least one burner body, being part of the at least one burner;    -   a spark plug body, connected to the at least one burner;    -   at least one gas connection pipe, being part of the gas feeding        circuit, to feed gas to the at least one burner;    -   a gas rail, being part of the gas feeding circuit, connected to        the support frame;    -   a connection member, being part of the gas feeding circuit, for        connecting the gas rail to an external feeding pipe; and    -   at least part of the support frame.

Preferably, at least two of said components are made as a single pieceof thermosetting or thermoplastic material.

The single piece may include at least part of the support frame.

In addition or in alternative, the single piece may include the at leastone burner body. Preferably, the at least one burner body includessupports for a thermocouple and a spark plug.

In addition or in alternative, the single piece may include the gasrail.

In addition or in alternative, the single piece may include the at leastone gas connection pipe.

In addition or in alternative, the single piece may include theconnection member.

In one possible embodiment, the gas cooking appliance comprises aplurality of burner bodies and a plurality of gas connection pipes, eachconnection pipe being designed to feed gas from the gas rail to acorresponding burner body, and the single piece includes all the burnerbodies and all the connection pipes.

The single piece may also include also a plurality of joints connectingwith each other different parts of the single piece.

In one possible embodiment, the support frame comprises a horizontalplate having at least one seat for hosting said at least one burner andthis plate is made of thermosetting or thermoplastic material.

In another possible embodiment, the support frame may comprise at leastone crossbar holding said at least one burner and this crossbar is madeof thermosetting or thermoplastic material.

The support frame may also comprise, on each side of the appliance, twovertical bars (one on the front side and one on the back side of theappliance) and two horizontal bars (one on the top side and one on thebottom side of the appliance) and, in one possible embodiment, thesevertical bars and/or these horizontal bars are made of thermosetting orthermoplastic material.

The gas cooking appliance may advantageously comprise a plurality ofburners, each burner including a burner body, and all the burner bodiesmay be made of thermosetting or thermoplastic material.

The gas feeding circuit may comprise a plurality of gas connection pipesto feed gas to said burners, and all the gas connection pipes may bemade of thermosetting or thermoplastic material.

In a further aspect thereof, the present invention relates to a processfor producing a gas cooking appliance comprising at least the followingcomponents:

-   -   a support frame;    -   at least one burner body;    -   a gas rail;    -   a spark plug body;    -   a connection member suitable to connect the rail to an external        feeding pipe to receive a gas; and    -   at least a connection pipe suitable to feed the gas from the        rail to the burner body;

the process comprising the step of moulding with a thermosetting orthermoplastic material at least one of said components and thenassembling together said components.

The step of moulding preferably comprises moulding together with athermosetting or thermoplastic material at least two of said componentsso as to form a single piece.

The same considerations made above, regarding the parts that can be madeof thermosetting or thermoplastic material and can be made as a singlepiece, are still valid for the production process.

Further features and advantages of the present invention will be moreevident from the following description of some embodiments, given onlyby non-limiting examples of the invention, with reference to the figureswherein:

FIG. 1 is a perspective view of part of a cooking hob (or cooktop)according to the present invention;

FIG. 2 is a top view of the same part of the cooking hob of FIG. 1;

FIG. 3 is an exploded view of a burner that is part of the cooking hobof FIG. 1;

FIG. 4 is a perspective view of the cooking hob of FIG. 1, in which alsoa top plate (or plateau) is shown;

FIG. 5 shows an elbow connection to connect part of the cooking hob ofthe present invention with an external feeding pipe; and

FIG. 6 is a perspective view of a free standing cooker a cooking systemaccording to the present invention.

FIGS. 1 and 2 show part of a gas cooking hob 1 according to a firstembodiment the present invention.

The hob 1 comprises a lower supporting frame (or plate) 2, a pluralityof burners 3 and a gas feeding circuit 4.

The supporting plate 2 is a cup-shaped planar rectangular body, layinghorizontally, designed to support a plurality of other componentsdescribed below.

The burners 3 are positioned in predetermined points of the frame 2. Inthe present embodiment there are four burners 3 positioned according tothe vertices of a square or a rectangle.

As shown in FIG. 3, each burner 3 comprises:

-   -   a burner body 5, which is held by the supporting frame 2, in        particular fixed to the frame 2;    -   a burner crown 6, held by the burner body 5 and having a        plurality of radiant openings on its circumference for the exit        of air-gas combustion mixture;    -   a cap 7, to close the burner top;    -   a Venturi-type central vertical tubular element (not shown) for        air/gas mixing, which in the present embodiment is integral with        the burner crown 6, but in a different embodiment could be also        a separate piece;    -   a gas injector 14 to eject a gas flow into the Venturi-type        element, and which can be integrated in the burner body;    -   a thermocouple 16, and related support 17 (integral with the        burner body 5 in the present embodiment); and    -   a spark plug 15, and related support 18 (integral with the        burner body 5 in the present embodiment).

With reference again to FIGS. 1, 2 and also to FIG. 5, the gas feedingcircuit 4 comprises:

-   -   a gas rail 8 extending along one side of the frame 2 and        suitable to be connected to an external gas feeding pipe (not        shown) to receive the combustion gas;    -   a connection member 19 (see FIG. 5), preferably of a “elbow”        type, to connect the gas rail 8 with the external gas feeding        pipe;    -   a plurality of valves 9 arranged along the gas rail 8, in a        number corresponding to the number of burners 3 (four in the        present embodiment), to regulate the gas flow;    -   a corresponding number of gas connection pipes 10, each        connecting a valve 9 to a burner 3 to feed it with the gas; and    -   a plurality of joints 11, to connect each other the gas rail 8        with the valves 9, the valves with the pipes 10, and the pipes        10 with the burners 3.

As shown in FIG. 4, the hob 1 also comprises a top plate (or work plate)12, which is arranged onto the lower supporting plate 2 to define therebetween a space where the gas feeding circuit is arranged. The top plate12 has a plurality of holes where the burners 3 can extend through. Thehob 1 further comprises a plurality of knobs 13 (only one of which isrepresented in FIG. 4) connected to the valves 9.

According to the present invention, some of the above-describedcomponents are realized in a thermosetting or thermoplastic material andare preferably made integral with each other in one piece by means of amoulding process. In particular, it is possible to realize differentembodiments, where the following parts can be selectively made of athermosetting or thermoplastic material by an injection mouldingprocess:

-   -   the supporting frame 2;    -   the burner bodies 5, possibly including the supports 17 and 18        for the thermocouple 16 and the spark plug 15, respectively;    -   the body of the spark plug 15 (insulation body);    -   the gas rail 8;    -   the elbow connection 19; and    -   the gas connection pipes 10 or part thereof.

Regarding the burner crowns 6 of FIG. 3, the Applicant has noticed thatthe high temperature to which it is subjected does not allow to use thethermosetting and thermoplastic materials known today.

Regarding the thermocouple 16, this part cannot be made of thermosettingand thermoplastic material because of the presence of electricalcomponents.

Regarding the valves 9, the complexity of this component does not renderit particularly suitable for a realization in thermoplastic orthermosetting material.

According to the present invention, it is also particularly advantageousto integrate in a single piece two or more of the above parts, by meansof a single moulding process. By way of non-limitative examples, thefollowing parts could be made integral with each other: the supportingframe 2 and the burner bodies 5, the supporting frame 2 and the gas rail8, the supporting frame 2 and the connection pipes 10 or part thereof,the gas rail 8 and the elbow connection 19, each burner body with atleast a part of the connection pipe 10.

It is also possible to make more complex combinations of the abovecomponents, and possibly also to make a single piece including all theabove components.

The parts that are not made in one piece can be assembled with the otherparts according to traditional fixing techniques. Moreover, the partsthat are not made in one piece can be made of thermosetting orthermoplastic material as well, by means of a separate moulding process,and then assembled with the others by means of traditional fixingtechniques.

The Applicant has found that the thermosetting and thermoplasticmaterials defined by the following ranges of parameters are particularlysuitable for the scope of the present invention.

Thermosetting materials Range of values Material Parameter TensileStrength 70-130 Mpa Linear Dilation Coefficient 10 · 10⁻⁶-30 · 10⁻⁶ mm °C. Flammability V0 Class Water absorption ≦0.5% HDT (heat deflectiontemperature) ≧220° C. Upper Limit Temperature Index ≧120° C. MouldingProcess Parameter Injection Temperature Equal to mould temperature Mouldtemperature 130-160° C. Injection time (*) Equal to stay time in themould Stay Time in the Mould 30-40 s/mm Cooling Time no cooling timeCompression Pressure 40-110 BAR Notes: (*) The injection time can bedefined as the polimerization time

Thermoplastic Materials Range of values Material Parameter TensileStrength 150-250 MPa Linear Dilation Coefficient 12 × 10⁻⁶-19 × 10⁻⁶ mm° C. Flammability V0 Class Water absorption <0.2% HDT (heat deflectiontemperature) 220-280° C. Upper Limit Temperature Index >150° C. MouldingProcess Parameter Injection Temperature >250° C. Mould temperature >100°C. Injection time (*) <4 s Stay Time in the Mould (**) about 40 s formaterial thickness ≧3 mm or about 10 s for each mm of material thicknessCooling Time about 10 s for each mm of material thickness InjectionPressare 800-1500 Bar Notes: (*) The injection time can be defined asthe polymerization time (**) Stay Time = Cooling Time + Injection Time +Machine Movement Time

FIG. 6 shows another type of appliance, in particular a free standingcooker 101, realized according to the present invention. The freestanding cooker 101 comprises a support frame 102, a plurality ofburners 103 rigidly connected, directly or indirectly, to the supportframe 102, and a gas feeding circuit 104.

The burners 103 can be made as previously described with reference toFIG. 3.

The support frame 102 comprises an assembly of elongated structuralelements placed vertically or horizontally along the perimeter of theappliance so as to form the skeleton thereof, to which the externalspanels, such as the side panels 151 of FIG. 6, and the various internalparts, are connected.

In particular, the supporting frame 102 could comprise, on each side ofthe appliance, two vertical bars 141 (one on the front and one on theback of the appliance) and two horizontal bars 142 (one on the top andone on the bottom of the appliance), forming respective rectangularbodies.

In the embodiment of FIG. 6, the support frame 102 also comprises twocrossbars 144 extending parallel to each other between the twohorizontal bars 142 so as to define supporting elements for the burners103. In particular, the burners 103 are rigidly connected to thecrossbars 144.

Some of the bars 141, 142 and 144, or all of them, may be made ofthermosetting and thermoplastic material. For example, in one possibleembodiment all the mentioned bars can be made of thermosetting andthermoplastic material, and in another possible embodiment only thecrossbars 144 is made of thermosetting and thermoplastic material whilethe bars 141 and 142 are made of another material, preferably metal.

The cooker 101 also comprises a top plate, not represented in FIG. 6,having substantially the same shape and function of the top plate 12 ofthe hob 1 previously described.

In a further possible embodiment, the two crossbars 144 may be missing,and the burners 103 may be directly held by the top plate. In thisembodiment, it is possible to make of thermosetting and thermoplasticmaterial all the bars 141 and 142, or possibly only some of them. Inthis case the burners 103 are rigidly connected to the support frame102, formed by the bars 141 and 142, through (i.e. by means of) the topplate.

The gas feeding circuit 104 comprises connection pipes 110, one for eachburner, a rail 108 similar to the one of the hob 1, and a connectionmember (not shown) to connect the gas rail with the external gas feedingpipe.

As in the case of the cooktop previously described, at least one, butpreferably more than one, of these components is realized in athermosetting or thermoplastic material. If two or more components aremade of thermosetting or thermoplastic material, these components can bepossibly made integral with each other in one piece by means of amoulding process. In particular, it is possible to make of athermosetting or thermoplastic material one or more of the followingcomponents:

-   -   the supporting frame 102 or part thereof;    -   the burner bodies 5, possibly including the supports for the        thermocouple and the spark plug, respectively;    -   the body 15 of the spark plug (insulation body);    -   the gas rail 108;    -   the connection member 19; and    -   the connection pipes 110 or part thereof.

It is clear that the embodiments and the materials previously describedare just illustrative examples and that numerous variants can be madewithout departing from the scope of the present invention.

For example, the burners could be made according to different designsknown in the art, such as with more than one flame crowns and a morecomplex structure. There can be also more than one injector. For thepurposes of the present invention, the injectors could be alsoconsidered as part of the gas feeding circuit and be integrated with theconnecting pipes. Moreover, the connector 19 can be of a different typethan an elbow connector.

The present invention offers several advantages over the prior art.

First, the production cost, and therefore the final cost of theappliance, is reduced, since it is possible to produce some parts of theapparatus by a simple and cheap moulding process, and the number ofparts to be assembled can be reduced. The thermoplastic component(s)made by the moulding process can be easily and quickly assembled withthe other parts, and this advantage provides benefit in both theproduction process and possible maintenance/repair process, where theapparatus must be disassembled and then assembled again.

It is also possible to have a wide variety of cheap coloured parts, byusing particular additives in the moulding composition, thus improvingthe aesthetic of the apparatus.

As concern the manufacturing process, no particular details have beenprovided, as the injection moulding and the assembling techniquespreviously mentioned are well known in the art.

1. A gas cooking appliance (1; 101), comprising a support frame (2;102), at least one burner (3; 103) rigidly connected to said supportframe, and a gas feeding circuit (4; 104) to feed gas to said burner,characterized in that at least one of the following components of thegas cooking appliance is made of a thermosetting or thermoplasticmaterial: at least one burner body (5), being part of said at least oneburner; a spark plug body (15), connected to said at least one burner;at least one gas connection pipe (10; 110), being part of said gasfeeding circuit, to feed gas to said at least one burner; a gas rail (8;108), being part of said gas feeding circuit, connected to said supportframe; a connection member (19), being part of said gas feeding circuit,for connecting the gas rail to an external feeding pipe; and at leastpart of the support frame (2; 102).
 2. The gas cooking appliance ofclaim 1, wherein at least two of said components are made as a singlepiece of thermosetting or thermoplastic material.
 3. The gas cookingappliance of claim 2, wherein said single piece includes at least partof the support frame.
 4. The gas cooking appliance of claim 2, whereinsaid single piece includes the at least one burner body.
 5. The gascooking appliance of claim 2, wherein said single piece includes the gasrail.
 6. The gas cooking appliance of claim 2, wherein said single pieceincludes the at least one gas connection pipe.
 7. The gas cookingappliance of claim 2, wherein said single piece includes the connectionmember.
 8. The gas cooking appliance of claim 2, wherein it comprises aplurality of burner bodies (5) and a plurality of gas connection pipes(10), each connection pipe being designed to feed gas from the gas railto a corresponding burner body, and wherein said single piece includesall the burner bodies and all the connection pipes.
 9. The gas cookingappliance of claim 1, wherein said single piece includes also aplurality of joints (11) connecting each other different parts of saidsingle piece.
 10. The gas cooking appliance of claim 1, wherein thesupport frame comprises a horizontal plate (2) having at least one seatfor hosting said at least one burner and wherein the plate is made ofthermosetting or thermoplastic material.
 11. The gas cooking applianceof claim 1, wherein it comprises a plurality of burners, each burnerincluding a burner body (5), and wherein all the burner bodies are madeof thermosetting or thermoplastic material.
 12. The gas cookingappliance of claim 1, wherein the gas feeding circuit comprises aplurality of gas connection pipes (10; 110) to feed gas to said burners,and wherein all of the gas connection pipes (10; 110) are made ofthermosetting or thermoplastic material.
 13. The gas cooking applianceof claim 1, wherein the support frame comprises at least one crossbar(144) holding said at least one burner and wherein the crossbar is madeof thermosetting or thermoplastic material.
 14. A process for producinga gas cooking appliance (1; 101) comprising at least the followingcomponents: a support frame (2; 102); at least one burner body (5); agas rail (8; 108); a spark plug body (15); a connection member (19)suitable to connect the rail to an external feeding pipe to receive agas; and at least a connection pipe (10; 110) suitable to feed the gasfrom the rail to the burner body; the process comprising the step ofmoulding with a thermosetting or thermoplastic material at least one ofsaid components and then assembling together said components.
 15. Theprocess of claim 14, wherein the step of moulding comprises mouldingtogether with a thermosetting or thermoplastic material at least two ofsaid components so as to form a single piece.